分类： 天文学 >> 天文学 提交时间： 2023-02-19
Nobuyuki Sakai
Bo Zhang
Shuangjing Xu
Daisuke Sakai
Yoshiaki Tamura
Takaaki Jike
Taehyun Jung
Chungsik Oh
Jeong-Sook Kim
Noriyuki Kawaguchi
Hiroshi Imai
Wu Jiang
Lang Cui
Soon-Wook Kim
Pengfei Jiang
Tomoharu Kurayama
Jeong Ae Lee
Kazuya Hachisuka
Dong-Kyu Jung
Bo Xia
摘要： We aim to reveal the structure and kinematics of the Outer-Scutum-Centaurus (OSC) arm located on the far side of the Milky Way through very long baseline interferometry (VLBI) astrometry using KaVA, which is composed of KVN (Korean VLBI Network) and VERA (VLBI Exploration of Radio Astrometry). We report the proper motion of a 22 GHz H$_{2}$O maser source, which is associated with the star-forming region G034.84$-$00.95, to be ($\mu_{\alpha} \rm{cos}\delta$, $\mu_{\delta}$) = ($-$1.61$\pm$0.18, $-$4.29$\pm$0.16) mas yr$^{-1}$ in equatorial coordinates (J2000). We estimate the 2D kinematic distance to the source to be 18.6$\pm$1.0 kpc, which is derived from the variance-weighted average of kinematic distances with LSR velocity and the Galactic-longitude component of the measured proper motion. Our result places the source in the OSC arm and implies that G034.84$-$00.95 is moving away from the Galactic plane with a vertical velocity of $-$38$\pm$16 km s$^{-1}$. Since the H I supershell GS033+06$-$49 is located at a kinematic distance roughly equal to that of G034.84$-$00.95, it is expected that gas circulation occurs between the outer Galactic disk around G034.84$-$00.95 with a Galactocentric distance of 12.8$^{+1.0}_{-0.9}$ kpc and halo. We evaluate possible origins of the fast vertical motion of G034.84$-$00.95, which are (1) supernova explosions and (2) cloud collisions with the Galactic disk. However, neither of the possibilities are matched with the results of VLBI astrometry as well as spatial distributions of H II regions and H I gas.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Phrudth Jaroenjittichai
Koichiro Sugiyama
Busaba H. Kramer
Boonrucksar Soonthornthum
Takuya Akahori
Kitiyanee Asanok
Willem Baan
Sherin Hassan Bran
Shari L. Breen
Se-Hyung Cho
Thanapol Chanapote
Richard Dodson
Simon P. Ellingsen
Sandra Etoka
Malcolm D. Gray
James A. Green
Kazuhiro Hada
Marcus Halson
Tomoya Hirota
Mareki Honma
摘要： This White Paper summarises potential key science topics to be achieved with Thai National Radio Telescope (TNRT). The commissioning phase has started in mid 2022. The key science topics consist of "Pulsars and Fast Radio Bursts (FRBs)", "Star Forming Regions (SFRs)", "Galaxy and Active Galactic Nuclei (AGNs)", "Evolved Stars", "Radio Emission of Chemically Peculiar (CP) Stars", and "Geodesy", covering a wide range of observing frequencies in L/C/X/Ku/K/Q/W-bands (1-115 GHz). As a single-dish instrument, TNRT is a perfect tool to explore time domain astronomy with its agile observing systems and flexible operation. Due to its ideal geographical location, TNRT will significantly enhance Very Long Baseline Interferometry (VLBI) arrays, such as East Asian VLBI Network (EAVN), Australia Long Baseline Array (LBA), European VLBI Network (EVN), in particular via providing a unique coverage of the sky resulting in a better complete "uv" coverage, improving synthesized-beam and imaging quality with reducing side-lobes. This document highlights key science topics achievable with TNRT in single-dish mode and in collaboration with VLBI arrays.
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